Capturing Condensable Gases with Ionic Liquids

Abstract

Ionic liquids (ILs) have been proposed to simultaneously capture a variety of condensable gases for the first time. The hydrophobic IL [EMIM][Tf2N] was selected as a suitable absorbent screened by the COSMO-RS (conductor-like screening model for real solvents) model, which in combination with the quantum chemistry calculation provided some theoretical insight into mechanisms with respect to condensable gas capture. Considering the simultaneous capture of volatile organic compounds (VOCs) and water, we selected benzene, toluene, and p-xylene (BTX) as three kinds of VOC representatives, measured the vapor–liquid equilibrium (VLE) of BTX + [EMIM][Tf2N] mixture systems, and compared them with the predicted results by the UNIFAC–Lei model. The experiment of capturing condensable gases with [EMIM][Tf2N] as the absorbent was conducted. Furthermore, the conceptual design of continuous processes with [EMIM][Tf2N] and the conventional benchmark solvent triethylene glycol as absorbents at the industrial scale was performed using a rigorous equilibrium stage model with the UNIFAC–Lei model parameter input. It reveals that condensable gas capture with an IL belongs to a typical process intensification technology in chemical engineering.